The invention relates to a valve seat - to - body connection that provides for positive fluid tight sealing of the connection, while still allowing ready removal of the valve seat and the particular valve seat utilizable therein. The replacement of valve seats for high pressure environments has long posed many problems in the art. Normally, the tighter the fit, the better the seal, however the tighter the fit, the harder it is to remove.
In order to alleviate some of the problems raised by providing valve seat - to - body connections in high pressure and temperature environments, some manufacturers carry seats in stock with four or more "press fit" size ranges, while other manufacturers weld in the valve seats (making repair prohibitive), and still others settle for seats that have a very limited service range. It has been suggested that other ways could be provided for effecting a tight seal between a valve seat and body (or associated members). For instance, U.S. Pat. Nos. 3,166,291, 3,421,733, 3,752,178, and 3,765,440 suggest the introduction of a material of plastic consistency behind rubber or Teflon seal members for providing a back-up seal, and for forcing the rubber or Teflon members into tighter fitting engagement. U.S. Pat. No. 3,374,261 suggests such an introduction of a special material into a seal area after seal failure has occurred in order to "patch up" the failed seal.
While all of the above proposals can result in an effective seal, none of them can provide a valve seat - to - body connection that is normally readily detachable (while still having enough securement to prevent the valve seat from falling out during installation), allowing ready replacement thereof, yet may be selectively tightly sealed to prevent ready removal thereof and prevent fluid leakage between the valve seat and valve body even under conditions of continuous high pressure and high temperature. According to the present invention a valve seat is provided for furnishing a metal to metal seal between a valve seat and valve body that is easy to replace and that has a wide service range, not being affected by temperature, pressure, chemical attack, aging, etc.
According to the apparatus of the present invention, a valve seat body member having first and second sections of different outside diameter is provided. The valve seat is adapted to be mounted in a valve body section having a predetermined inside diameter slightly larger than but generally corresponding to the outside diameter of the first section of the valve seat member. A resilient metallic ring, preferably of tubular cross-section, is disposed around the second section of the valve seat member, the metallic ring having an inside diameter slightly greater than the outside diameter of the second section of the valve seat member, and having an outside diameter slightly greater than the inside diameter of the valve body section in which the valve seat member is mounted. When the valve seat member is inserted into the valve body, the metallic ring retains the valve seat member within the valve body, although the retention forces are relatively small, and the seat member can be readily detached. When it is then desired to seal the connection for operation under conditions of high pressure and temperature a material of plastic consistency or the like is then injected under pressure into the area surrounding the metallic ring (preferably the second section of the valve seat member is adjacent several different faces of the valve body), thereby deforming the resilient metallic ring and causing it to provide a fluid-tight metal-to-metal seal between the valve seat member and the valve body.
According to a method of using the apparatus the present invention, a metallic ring as described above is placed around a second section of a valve seat member, the valve seat member is inserted into a valve body (while remaining readily detachable therefrom), and the metallic ring is deformed by applying a material of plastic consistency or the like to the area surrounding the metallic ring, thereby providing a fluid-tight seal between the valve seat member and the valve body. The seat member may then again be made readily detachable by relieving the pressure of the plastic material or the like in the ring area.
It is the primary object of this invention to provide an improved valve seat - to - body seal, and installation thereof. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.